Has anyone heard of temporary tongue stiffness brought on by exercise?

Twice in the past week this happened. The first time I was on a bike trail, just starting up a hill and suddenly felt this strange feeling in my mouth like never before. I kept going and on the downhill the feeling went away and I continued on a one hour ride with no more problems.
Then yesterday I was on my exercise bike for about 6 minutes, paused for a minute to make an adjustment, and kept going. Suddenly I noticed a strange feeling again. This time I spoke to my wife who was in the room and immediatly felt like my tongue was partially paralyzed! I could barely talk and it sounded like I was a spastic person. I halted the exercise and sat down. All feeling and normality returned in about 4 minutes!! Tried to look this up and the closest thing I could find is Dysarthria. But nothing relates it to exercise. Anyone have an idea what is wrong? I am 74.